The performance for paging in DevForce will never be great, but we have done what we can to make it as fast as possible, In fact, for the DevForce 3.4.0.3, we have added some performance optimizations to make performance quite similar to standard RdbQueries in many cases..
The best thing you can do to improve performance is to reduce the "width" of your query. In other words, rather than returning all of the columns in each row (which is standard), construct a light weight Dynamic Entity that is composed of just a few columns. For example. for Orders, create a Dynamic Entity of Id, Customer Id, and OrderDate so that your fetch returns 3 columns instead of 20. If you are unfamiliar with Dynamic Entities, there is a Tutorial on this feature as well as some good material in the Developer's Guide.
However, reducing the width of your query is generally not recommended. The reason for this is that the Dynamic Entity contains only some of the columns of the underlying entity. Therefore, only consider decreasing the width if performance is all important and you will likely not be doing extensive editing operations.